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一、加法运算律的再延伸我们在计算几个加数连加时可把能够相加得整十、整百、整千……的加数运用加法交换律、结合律改变运算顺序,使具有这类特征的加数优先计算。用字母表达的形式是:a+b+c=a+(b+c)。这样的法则在只有加减法混合的算式里也同样适用。在一道加减混合的算式中,如果有加数减减数能得整十数、整百数、整千数……我们也可以用这个加数先和减数相减,再和另一个加数相加。用字母表示:a+b-c=a-c+b=bc+a。运用这样的法则常常会给我们的计算带来事半功倍的效果,提高计算的
First, the law of the re-extension of the addition operation We can calculate the number of plus-plus-plus can be added to the whole ten, a hundred, a thousand ... The addition of the use of additive exchange law, combined with the law to change the order of operation, The sums of such features are given priority. The alphabetic form is: a + b + c = a + (b + c). This rule applies equally to addition and subtraction. In an algebraic addition and subtraction formula, if there is a plus minus the number of decimals can get the whole number, the whole hundred, the whole number of thousands ... ... We can also use the sum of the first and subtraction, and then plus another Add together. Letters: a + b-c = a-c + b = bc + a. The use of such rules often results in a multiplier effect on our calculations and increases the computational